1. Field of the Invention
The present invention relates generally to a method and apparatus for machining an electrically conductive film, and more particularly to a method and apparatus for removing portions of an electrically conductive film formed on an insulating substrate for patterning electrodes on the surface of the insulating substrate that forms part of a touch panel, a liquid crystal panel, or the like.
2. Description of the Related Art
Conventionally, touch panels have been used as means for users to input information to a variety of electronic devices. In addition, liquid crystal panels have been used as display means associated with electronic devices. Such touch panels and liquid crystal panels are constructed such that a pair of insulating substrates having transparent electrodes, each made of a transparent conductive film, formed on respective surfaces thereof are bonded so that the transparent electrodes are opposite to each other. In addition, for a touch panel, the pair of substrates are arranged in opposition with a spacer having a predetermined height (for example, 9-12 .mu.m) interposed therebetween to prevent the transparent electrodes from contacting each other in a normal state.
The respective transparent electrodes formed on the surface of the insulating substrate are separated by slit-like gaps to prevent adjacent transparent electrodes from contacting each other. Conventionally, the transparent electrodes on the insulating substrate have been formed mainly by a photolithographic method including etching processing. The photolithographic method involves forming an electrically conductive film over an entire surface of an insulating substrate by vacuum deposition or the like, forming a resist pattern on the electrically conductive film, and then removing exposed portions of the electrically conductive film by an etchant which dissolves such exposed portions.
The use of the photolithographic method, however, is not so favorable from a viewpoint of environmental preservation, because the photolithographic method involves wasted photoresist developing solution, etchant and so on.
In addition, when a pattern and/or shape of transparent electrodes are to be changed, a mask must be newly created from the photolithographic method, so that the photolithographic method experiences a low machining efficiency, and difficulties in supporting multi-product small-amount production and reducing the cost. Particularly, even the formation of several slits through an electrically conductive film on an insulating substrate as is the case of a hybrid type touch panel requires the same photolithographic process as a digital type touch panel which involves the formation of several hundred slits. Therefore, reduction in waste liquids and cost has been difficult although conductive film are machined only in small areas.
As a method and apparatus for machining an electrically conductive film that are free from the need for a waste liquid treatment, which has been involved in the photolithographic method including etching processing, inexpensive, and suitable for multi-product small-amount production, it is contemplated that a laser beam is irradiated as an energy beam. However, experiments and so on diligently conducted by the present inventors on the machining of a electrically conductive film with the laser irradiation have revealed that an energy distribution on the cross section of laser light may cause troubles such as irregular widths and undulated shapes of machined slits, a portion of conductive film left unremoved, a deeply excavated insulating substrate at a position corresponding to the center of laser light, and so on.
It should be noted that the above-mentioned troubles such as variations in machined dimensions, partially unremoved conductive film, damaged insulating substrate and so on could be experienced not only when an electrically conductive film is irradiated with the laser light for machining but also when it is machined through irradiation with a light beam other than a laser beam, and other energy beams such as an X-ray beam, a charged particle beam and so on.